The present invention relates to a fluid connection device with no dead volume, which is intended for transferring a fluid, and also to an automated system and method for continuously taking a series of liquid microsamples in such a way that the samples thus taken are in discrete packets in space and in time as far as their temporary storage container, for subsequent treatment. The invention applies more particularly, but not exclusively, to a fluid connection device for transferring whole blood microsamples from a mammal, for example a rat or a mouse.
The fluid connection devices that are used both in medicine and biology in relation with a catheter or the like, on the one hand, and with a flexible microtube, on the other hand, are usually standardized connectors of the “Luer” type defined by the ISO 594-1 standard of 1986 or else of the “Luer-lock” type defined by the ISO 594-2 standard of 1998. Referring to FIG. 2 appended to the present description, the usual connection devices 20′ essentially comprise:                a female fluid connector 22′ into which a catheter is pressed, said connector having a conical internal fitting surface 23′ that converges on a female end 24′ into which this catheter opens; and        a male fluid connector 25′ which is fitted into the female connector 22′ via its conical external surface 26′ which has the same conicity as the internal surface 23′ of the female connector and converges on a male end 27′ leaving, in the state of maximal insertion, a distance dl from the female end 24′ (see FIG. 2).        
Table 1 below lists the main dimensional characteristics of Luer connection devices (6% conicity angle) depending on the material used, according to the aforementioned standard.
TABLE 1Dimensions (mm)DimensionalRigidSemirigidparameterDescriptionmaterialmaterialBasedminMinimum diameter of3.9253.925dimensionsthe end of the maleconical connector(referencediameter)dmaxMaximum diameter of3.9904.027the end of the maleconical connectorDminMinimum diameter of4.2704.270the opening of thefemale conicalconnectorDmaxMaximum diameter of4.3154.315the opening of thefemale conicalconnectorEMinimum length of7.5007.500the male conicalconnectorFMinimum depth of7.5007.500the female conicalconnectorOtherL*Minimum penetration4.6654.050dimensionsM*Variance over the0.7500.750penetration of thefemale connectorN*Variance over the1.0831.700penetration of themale connectorR**maxRadius of curvature0.50.5With reference to the symbols * and ** of this table:*the dimensions L, M, N result from the base dimensions; and**or equivalent entry chamfer not having sharp angles.
A major drawback of the connection devices defined by the aforementioned standards is that the distance dl (typically about 3 mm) between the respective ends of the male and female connectors generates an intrinsic dead volume that becomes detrimental in various circumstances. The most frequent occurs when the connectors are used for circulating very small liquid samples, of the order of magnitude comparable to or even smaller than this dead volume. To give an example, when injecting or taking mammal blood microsamples, it is general practice to use a flexible line provided with a connector having a diameter of about 4 mm, the space thus delimited determining a dead volume of around 15 μl to 30 μl, which may cause the following problems in use:                since several successive microsamples serve to fill said dead volume, this delays the passage of the first microsamples and means that a larger volume of fluid is taken, which is lost; and        since the cross section of the fluid line is considerably enlarged owing to this dead volume, various microsamples become mixed up with one another, which is detrimental if the fluid is a liquid, and these microsamples are used subsequently, for example for the purpose of analysis. This impairs their traceability and is particularly prejudicial in the case of monitoring rapid biological phenomena during which it is of fundamental importance for each microsample to be able to retain its initial characteristics over the entire length of the distribution line.        
Other drawbacks may also result therefrom, such as a need to purge the line if it is desired to avoid any mixing with a residual fluid, this purging operation being moreover particularly difficult to carry out owing to the existence and the shape of the dead volume.
Known elsewhere, from the document U.S. Pat. No. 4,966,588, is the use, for injecting a therapeutic liquid substance, of a fluid connection device essentially comprising:                a male connector fitted into a female connector via respective cylindrical fitting surfaces provided with shoulders, this female connector being intended to receive a cannula forming an injection tip; and        a rigid injection needle that is inserted so as to pass through both the male connector and the female connector and also the cannula, by piercing a sealing washer positioned between the two connectors, and which is intended to be implanted into the body to be treated.        
A major drawback of this device employing a rigid injection needle that passes right through the connectors and the cannula lies in the small diameter of this needle compared with that of the opening of the male connector. Another drawback arises from the fact that the sealing washer may be unintentionally displaced following removal of the needle from the connectors after injection. This may cause positioning problems in the case of multiple use, or else may mean that the sealing washer, which is difficult to access, has to be changed at each use.
Finally, another drawback lies in the fact that the needle that perforates the sealing washer necessarily has a certain length, which may become problematic upstream or downstream of the needle. Thus, it is not at all suitable for injecting a liquid or for removing blood samples in a small mammal, such as a rat or mouse. In particular in rats, it is general practice to use the caudal vein of the animal (or, for injection, the caudal artery) by introducing a catheter directly connected to the flexible line via a connector. Introducing a metal needle of a certain length through the sealing washer assumes that this needle protrudes into the vein (or the artery), which can then be damaged when the animal moves its tail.